Gene Dosing and Imprinting Flashcards
(25 cards)
What is the name given to inactivated X chromosomes that are seen microscopically?
Barr bodies
What is uniparental disomy?
When to imprinting for one chromosome region is copied to the other leaving only maternal or only paternal imprinted genes
What is the pattern of passing down of gender specific imprints to gametes?
Female imprinted genes are passed to oocytes while male imprinted genes are passed to sperm
What causes Bechwith-Wiedemann syndrome?
60% is epimutation in maternally imprinted alleles
Which X-chromosome is inactivated in females, the maternally or paternally inherited one?
Both, it’s different in different cells
What does parthenogenetic refer to?
Receiving two maternally imprinted alleles for a gene
Epimutation results in what?
Loss of gender imprinting
What does bi-allelic expression refer to?
Alleles for a gene are expressed on both chromosomes
Which chromosome is replicated in Down syndrome?
21
What is the mechanism for inactivating an X-chromosome in females?
DNA methylation
Hyperchromatin structure
Non-coding RNAs
What does loss of heterozygosity refer to?
Microdeletion of one allele containing the imprinted genes
What is genomic imprinting?
Whereby the parental origin of a particular gene is marked by reversible epigenetics
What is the result of most trisomy’s?
Miscarriage
What trisomy is the cause of Edwards syndrome?
18
What is the name for this condition with this karyotype, 45,X
Turner syndrome
In which chromosome pair is a monosomy viable?
The sex chromosomes
What is haploinsufficiency?
Where one copy of a gene is insufficient to support normal cell function therefore fetal development
What is aneuploidy?
Unbalanced set of chromosomes
Apart from intellectual disability what is the major deficit in Down syndrome patients?
Congenital heart disease
What causes Prader-Willi syndrome?
Deficiency of paternal expressed genes
How does Edwards syndrome present?
Characteristic overlapping fingers and club-like hand
Congenital heart disease
Development disability
What causes Angelman syndrome?
Deficiency in maternally expressed genes responsible for AS
What does androgenic refer to?
Receiving two paternally imprinted alleles for a gene
What is the most common cause of aneuploidy?
Chromosome non-disjunction of homologous chromosomes - failure of a chromosome to separate into a new cell during cell division
